This is an application for 4 1/2 years of support for the clinical center at Wills Eye Hospital to continue participation in the ongoing multicenter Advanced Glaucoma Intervention Study (AGIS). The principal goal of AGIS is to assess systematically the long-range outcomes of sequences of interventions in eyes with primary open-angle glaucoma that have failed initial medical treatment. Between April 1, 1988 and March 31, 1991 AGIS has enrolled 575 eyes of 435 patients. Each eye has been randomly assigned to one of two intervention sequences: 1) trabeculectomy (T) followed by argon laser trabeculoplasty (ALT) should T fail and followed by a second T should ALT fail; and 2) ALT followed by T should ALT fail and followed by another T should the first T fail. The interventions are supplemented with medical treatment as needed. As of March 31, 1991 follow-up ranged from 0 to 36 months. Less than five percent of follow-up exams, scheduled at 6-month intervals, have been missed. Data are being collected on visual function loss, intervention failure, complications, need for supplemental medical therapy, compliance with medical therapy, and quality of life. The prognostic values of ocular and non-ocular medical factors and personal factors are being studied. The study plans 1 ) to continue patient recruitment -until 790 eyes are enrolled, a goal that is expected to be reached between April 1 and November 30, 1992, and 2) to continue patient follow-up until November 30, 1996, so that follow-up will ultimately range from a minimum of 4 to 4 2/3 years to a maximum of 8 2/3 years. A coordinating center collects, processes, and analyzes study data and coordinates study activities. A Policy and Treatment Effects Monitoring Board supervises the conduct of the study and monitors study outcomes. Submitted with the Georgetown University lead application are: 1) the AGIS research plan, detailing study rationale, design, and methods, 2) the plans for continued patient recruitment and follow-up, and 3) study accomplishments to date, including examples of data analyses. Between April 1, 1988 and March 31, 1991 this clinical center has enrolled 72 eyes of 49 patients. The present application details the qualifications of this clinical center for continued participation, including our ability to recruit and retain patients and to adhere to the study definitions, criteria, and procedures.